1. Field of the Invention
The present invention relates to a new and improved apparatus for the removal of disturbing or spurious substances, especially printing ink from waste paper suspensions.
Generally speaking, the apparatus of the present development for the removal of disturbing or spurious substances, especially printing ink from waste paper suspensions, is of the type comprising at least one fillable container provided with infeed or inlet openings through which there can be introduced the stock suspension to be cleaned, which is admixed with air bubbles, at locations situated beneath the level of the stock suspension in the filled container. An aeration device for the stock suspension is constituted by stepped diffusors where, at the region of a step jump or transition, the air can be sucked in or pressed or forced in. The container is provided with a dam-up or retardation device having an upper edge over which there can be removed the flotation foam or froth containing the disturbing substances. At least one good stock withdrawal or outfeed line is provided at the container beneath the infeed or inlet openings for the stock suspension to be cleaned, through which the cleaned stock suspension can be removed from the container.
2. Discussion of the Background and Material Information
Such type of flotation apparatuses, especially when processing stock suspensions produced from waste paper, serve to eliminate disturbing or spurious substances including printing ink particles therefrom. Thus, as is known in this technology, air bubbles are admixed into the stock suspension which, in the flotation stage, usually in conjunction with admixed chemicals, form a foam or froth containing the disturbing substances or contaminants which is then removed. Stepped diffusors have been found to be useful for producing the air bubbles and for the admixing thereof with the stock suspension. This is so, because such stepped diffusors promote both the sucking in of air and also the formation and distribution of the air bubbles.
A known flotation apparatus of the aforementioned type has been disclosed, for instance, in the commonly assigned German Petty Patent No. 9,007,266, granted Oct. 11, 1990.
However, in known flotation apparatuses it has been repeatedly determined that the flotation operation does not eliminate all of the disturbing particles which are basically capable of undergoing flotation. In particular, it has been found that the range of the grain size, of the actually eliminated disturbing particles is smaller than the range of the grain size of the disturbing particles actually present in the stock suspension.